This invention relates to a process for the refining of wheat based on the combined use of dry milling and wet milling procedures, and using a unique wet milling sequence, to obtain high quality wheat starch and an animal feed.
A wheat kernel consists of three major components: (i) a fibrous outer layer or wheat bran, (ii) germ, and (iii) endosperm. The endosperm contains two important ingredients, wheat starch and wheat gluten. Wheat starch has a wide variety of applications, including its use as a constituent in adhesives and in paper making, as a food thickener, and as a source of dextrose sugar and other food sweeteners. Wheat gluten, in its naturally occurring "vital" form, can be admixed with water to form a cohesive, pliable mass which is useful in the preparation of bakery goods.
A variety of methods for refining whole wheat are known. In the more conventional processes, which are based on the use of dry milling techniques, the bran and germ are separated from the endosperm while in the dry state, and the endosperm is dry ground into fine particles, i.e., wheat flour. The wheat flour is then refined further to obtain wheat starch and wheat gluten. Commercially, the separation of starch and wheat gluten from flour is commonly effected by forming the flour into a dough or batter, mechanically consolidating the gluten into solid masses and washing away the starch. Typically, the germ and bran are discarded as undesirable by-products.
More recently, wheat refining processes based on the use of wet milling techniques have been proposed. In general, whole wheat kernels are soaked in water to soften, or "temper" the wheat kernel, the soaked kernel is milled to split the outer layer and to remove at least the bran, and the resulting endosperm or endosperm and germ is treated further to obtain a baking dough or separated into a starch fraction and a protein (gluten) fraction. See, e.g., Rodgers et al U.S. Pat. No. 3,851,085, Galle et al, U.S. Pat. No. 3,958,016, Durst, U.S. Pat. No. 3,788,861 and Rao et al, U.S. Pat. Nos. 3,790,553, 3,979,375 and 3,891,613.
In German Offenlegungsschrift No. 2,642,628, there is disclosed a process in which wheat is dry milled to separate endosperm fractions from the kernel, the endosperm is dispersed in water, and the aqueous dispersion is separated by centrifuging into a starch-rich fraction and a gluten-rich fraction.